A Precision Low-TC Wide-Range CMOS Current Reference

This paper describes a programmable temperature-compensated CMOS current reference. The proposed circuit achieves a first-order temperature compensation by canceling the negative temperature coefficient (TC) of an on-chip poly resistor with the positive TC of a MOS transistor operating in the ohmic region. Programmability of the current reference is enabled with the use of floating-gate transistors, thus allowing arbitrary current values to be set accurately. The temperature compensation is independent of the reference value; a low TC reference is possible for a wide range of currents. Prototypes from a 0.5 mum CMOS process exhibited a maximum temperature coefficient of 132 ppm/degC for a temperature range of 0degC to 80degC. Experimental results showed a current precision of 0.02% along with a line regulation of 1%/V for a supply voltage of 2.3 V to 3.3 V. These results were obtained for current references of 16 muA to 53 muA for five different prototypes.